As was pointed out, WASAT AL-DAR simply means either "middle of the house" or "in the middle of the house." In other words, WASAT is sometimes used as a noun, other times as a preposition. Based on your description of the German text, the author is probably using the term as a noun.

The inner courtyard in a riad is called JARDA. The expression WASAT AL-DAR is not a name, but merely a description. There is no need for phonetically transcribing the Arabic description in a German or English text. The author is either confused, thinking it the Arabic name of the inner courtyard, or is simply following the grand tradition of Orientalism, where writings are peppered by untranslated Arabic terms to give the subject matter a wholly exotic flavor, or to show off the author's knowledge of Arabic. This is similar to using the Arabic word ALLAH in reference to God whenever the context is Islamic. Do you remember how American reporters referred the Iranian parliament as the "majlis" during the hostage crisis? The idea is to make it sound outlandish.

I suggest "inner courtyard."


Fuad